The present invention is directed to a rewinder for thin tapes, especially those tapes used for supporting a metal foil which is being processed in a machine for processing sheet-like material, such as boards, paper and plastic.
A converting machine, which is designed, for instance, for hot or cold application of a metallized film, in accordance with one of several images on a sheet-like material being processed in the machine, generally includes at least one unwinding device for foil tapes, and means for unrolling the tape intermittently in such a way as to allow its surface to be utilized optimally and a mechanism for rewinding the remaining foil tape after the transfer.
Among the known devices for foil tape rewinding is a terminal wind-up reel which receives the foil tape. Currently the trade uses several foil tapes which extend parallel throughout the machine operating width. This arrangement compulsorily entails the use of the same number of terminal wind-up reels as foil tapes being used. Thus, for instance, if four foil tapes are used, four terminal wind-up reels will be necessary and will be positioned pairwise on two crosswise pivoting bars secured between the frames of the converting machine.
Every terminal wind-up reel is connected to its pivoting bar by means of a lever arm. The terminal wind-up reels are driven by means of two rotary shafts, which are arranged to extend crosswise between the frames of the converting machine. The circumference of these rotary shafts will make contact with the circumference of the circular lateral guides of each of the terminal wind-up reels which procedure involves a continuous frictional driving action. The different rates of advance of various foil tapes, thus, causes irregular rotation of the terminal wind-up reels. This means that, in certain cases, a terminal wind-up reel will be rotated, whereas another, for example one in which the foil tape is not being pulled forward, will remain motionless and have its circumference rubbing against the surface of the rotary shaft.
The designs mentioned above have certain drawbacks, for example they can only be arranged within the machine, which causes difficulty in obtaining access to the various terminal wind-up reels and increases the down-time of the machine when a fully rewound or filled reel has to be replaced by an empty reel. Another drawback is that, on account of the design of the terminal wind-up reel frictional drive, there is no possibility of avoiding a friction between the circumference of the reel and the rotary shaft, which will cause, in certain cases, a build-up of an undesired polish or smoothing of the contact surfaces. Such a polishing or smoothing of the contact surfaces can interfere with the frictional drive and result in a compromising of the desired tension on the foil tape on the occasion of its advance. In this connection, the wear of the circumferential parts of the reels should also be given consideration.